Filter plate



May 8, 1928.

H. L. WATSON FILTER PLATE Filed Jan. 3l, 1924' UU (10 w"un" Jm/eneo/Tfilter but other forms may be used. I preferlatented Maly '8, v UNITEDSTATES HABOLI L. WATSON, l

N 1,669,362A PATENT oFFicE-.j

0F LYNN, MASSACHUSETTS, 'ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION 0F YOR'K.

FILTER PLATE'.

pplication iled January 3.1, 1924. Serial No. 689.825.

The present invention co-uqu-ises a new filtering medium which ismechanically strong, resistant to the action of chemicals and possessesa degree of porosity adapted for the rapid filtering ot liquids andgases.

This new filtering-medium is constituted essentially by particles ofporous silica te mented to one another by incipient-fusion.

Then silica has been employed for the manufacture of iilter plates, theparticles of silica have been cemented, together, by a binder of glass.For some .purposes the glass [binder is undesirable as itis soluble insomel It also -reduces of the media to be' filtered. the porosity of themass.`

I have discovered that by careful heating,

substantiallypure silica may be ritted to gether without the use of abinder .to form strong, coherent plates or other desired til-` teringbodies. My invention includes both a new silica product and the processof 1nak` ing such product.

The accompanying drawing shows in Fig.

1 in perspective a filter plate of silica which i embodies my invention;and Fig. 2 shows an' enlargement of a section of the surface of thematerial.

In carrying out my'invention, vsubstantially pure sand,' crushed quartzor other suitable form of silica is formed to desired shape in a mold ofcarbon, or othersuitable Arefractory material whichg-is' inert with resnect to silica. Fig. 1 shows a 'di'sc or plate to use particles passinga screen of about 510 mesh and 'retained by a screen of 60 mesh. Themass of silica is heated while` in said mold to a temperature of about1700 degrees centigrade in an electric resistance furnace or othersuitable heating means. The heating temperature should behigh enough tocause conversion of the silica it crystalline to the glassy state andtheadhesion or fritting of the silica particles to each other, but not sohigh as to cause such eoalescenceand glazing of the quartz as wouldsubstantially reduce-the porosity'of -the mass.

When a massof quartz whichA hasybeen heated to aboutf1700 degreescentigrade is taken from the furnace while still heated to A atemperature of about- 200 degrees centigrade. the surface of the,Yquartz has a grayish, glassy appearance. Upon coolmgl down 4to about 100degrees centigrade, a change 1n physical structure may be seentakingplace 1n the quartz, the exterlor surface becomes white and frostylooking, as though a checking or crackingof the quartz or con# versionto a lessvitreous condition were taking place.

As shown ininagniie'dformin Fig. 2, the

product consists of grains 1- frtted together by incipient Afusion attheir edges` leaving cavities 2 between the grains. particles have the'appearance of havingvbecome intulnescent` and exploded somewhat likepulled grain. -They are weak and friable mechanically.

The product is'a strong, coherent mass having a mass density materiallylower than thatof silica and being sufficiently porous to permit liquidsand gases to rapidly Aflow therethrough.

Various corrosive liquids may be filtered by this new product withoutchemical attack,

even hotconcentrated alkalies may be fil- .tered without appreciableattack ofthe silica.

IVhat I claim asnew and desire to secure i by Letters Patent'of theUnited States, is:

1. A cellular body comprising particles of silica adhering to oneanother in tlie absence of abinder, said particles being individuallyexpanded into an intumescent condition Vrc. sembling puffed grain.

2. A' filter for liquids and gases -constituted of intumescent .silicaparticles a.dher.

rlhe silica A 'zoA ing to one another by incipient fusion in the absenceof a binder,'said tilterhaving materially lower mass. density thanordinary silica. A

3. The method of making ay porous, silica body which consists in heatinga mass of silica particles to a temperature at which adhesion loccurswithout complete fusion and then-cooling before coaleseence and glazing'ofsaid mass has occurred.

milioni) L, WATSON.

